Magnetic detection device having a plurality of first and second magnetoresistive elements

Abstract

A compact magnetic detection device with a high sensitivity. The device includes a single bias magnet producing a magnetic field to a gear having a magnetic substance, and a magnetoresistive effect element. The element is arranged so as to oppose the bias magnet and adjoin a pole face of the magnet on the gear's side. Further, the element is arranged in a plane substantially perpendicular to a moving direction of the gear, for producing resistance change caused by changes of magnetic field in response to the movement of the gear. Thus, the bias magnetic field existing in the moving direction of the gear is modulated to the direction facing the gear. Since a magnitude of modulation against the bias magnetic field amounts to a maximum in the vicinity of the pole face of the bias magnet on the gear's side, it is possible to realize the high sensitivity and furthermore, the magnetic detection device can be miniaturized by use of the single magnet.

What is claimed is: 
     
       1. A magnetic detection device, comprising: a bias magnet producing a magnetic field to an object having a magnetic substance; and   magnetoresistive means, arranged so as to oppose said bias magnet and adjoin a pole face thereof on a side of said object and arranged in a plane substantially perpendicular to a moving direction of said object, for producing a change of resistance by a change of the magnetic field in response to a movement of said object,   wherein said magnetoresistive means comprises a first magnetoresistive means including a plurality of first micro-magnetoresistive elements juxtaposed along a first direction facing said object and connected with each other in series, said plurality of first micro-magnetoresistive elements respectively forming elongated patterns extending in a second direction generally perpendicular to the first direction,   wherein a width of said plurality of first micro-magnetoresistive elements in the first direction is smaller than a dimension of said elongated patterns in the second direction by a predetermined length, and   wherein said magnetoresistive means further comprises a second magnetoresistive means connected to said first magnetoresistive means in series and arranged adjacently to a pole face of said bias magnet on the side of the object, said second magnetoresistive means including a plurality of second micro-magnetoresistive elements juxtaposed along the second direction and which respectively form patterns extending in the second direction with a dimension substantially equal to the width of said plurality of first micro-magnetoresistive elements.   
     
     
       2. A magnetic detection device as claimed in claim 1, wherein said plurality of first micro-magnetoresistive elements include a terminal to which an electrical power is supplied. 
     
     
       3. A magnetic detection device as claimed in claim 1, wherein said second micro-magnetoresistive elements include a ground terminal. 
     
     
       4. A magnetic detection device as claimed in claim 3, wherein said magnetoresistive means is provided, between said plurality of first micro-magnetoresistive elements and said plurality of second micro-magnetoresistive elements, with an output terminal of the magnetic detection device. 
     
     
       5. A magnetic detection device as claimed in claim 1, wherein said magnetoresistive means further comprises: a third magnetoresistive means connected to said second magnetoresistive means and arranged so as to extend along the second direction and adjoin the pole face of said bias magnet on the side of the object, said third magnetoresistive means having a form identical to that of said first magnetoresistive means; and   a fourth magnetoresistive means connected to said third magnetoresistive means and said first magnetoresistive means and arranged so as to extend along the second direction and adjoin the pole face of said bias magnet on the side of the object, said fourth magnetoresistive means having a form identical to that of said second magnetoresistive means.   
     
     
       6. A magnetic detection device, comprising: a bias magnet configured to produce a magnetic field toward an object having a magnetic substance; and   a magnetoresistive mechanism configured to produce a change of resistance corresponding to a change of the magnetic field caused by a movement of the object, and being arranged so as to oppose the bias magnet and adjoin a pole face of the magnet facing a side of the object and being arranged in a plane substantially perpendicular to a moving direction of the object, said magnetoresistive mechanism including:   a plurality of first micro-magnetoresistive elements juxtaposed along a first direction facing the object and connected with each other in series, said first magnetoresistive elements respectively forming elongated patterns extending in a second direction generally perpendicular to the first direction; and   a plurality of second micro-magnetoresistive elements connected to the plurality of first micro-magnetoresistive elements and being juxtaposed along the second direction and which respectively form patterns extending in the second direction with a dimension substantially equal to the width of the plurality of first micro-magnetoresistive elements,   wherein a width of the plurality of first micro-magnetoresistive elements in the first direction is smaller than a dimension of said elongated patterns in the second direction by a predetermined length.   
     
     
       7. A magnetic detection device as claimed in claim 6, wherein the plurality of first micro-magnetoresistive elements include a terminal to which an electrical power is supplied. 
     
     
       8. A magnetic detection device as claimed in claim 6, wherein the plurality of second micro-magnetoresistive elements include a ground terminal. 
     
     
       9. A magnetic detection device as claimed in claim 6, further comprising: an output terminal disposed between the plurality of first micro-magnetoresistive elements and the plurality of second micro-magnetoresistive elements.   
     
     
       10. A magnetic detection device as claimed in claim 6, wherein said magnetoresistive mechanism further comprises: a plurality of third micro-magnetoresistive elements connected to the plurality of second micro-magnetoresistive elements and arranged so as to extend along the second direction and adjoin the pole face of the bias magnet on the side of the object, the plurality of third micro-magnetoresistive elements having a form identical to that of the plurality of first micro-magnetoresistive elements, and   a plurality of fourth micro-magnetoresistive elements connected to the plurality of third micro-magnetoresistive elements and the plurality of first micro-magnetoresistive elements, and arranged so as to extend along the second direction and adjoin the pole face of the bias magnet on the side of the object, the plurality of fourth micro-magnetoresistive elements having a form identical to that of the plurality of second micro-magnetoresistive elements.